This is War

This Is War is the third studio album by Thirty Seconds to Mars, originally released on December 8, 2009 through Virgin Records. It was the band's first studio album in four years, after the breakthrough of their previous work, A Beautiful Lie (2005). The album was recorded over a span of two years while the band was in the midst of a legal dispute with Virgin over an alleged breach-of-contract. The case was later settled in April 2009, and the band signed to EMI later that year.

The album marked a departure from the band's previous material, implementing a more experimental direction that draws influence from progressive rock, new wave, industrial, and heavy metal music. Lyrically, it is a conceptual record shaped by the band's personal struggles and legal battle with their record label, and is sometimes considered a rock opera.